Time: 11:30 am Buffet, Noon Speaker Presentation

RSVP online by Friday, November 9th at noon on the FWGS website www.fwgs.org.

Cost: $27 with RSVP, $30 with no RSVP, student members eat free with RSVP (Student Members please directly email the FWGS Secretary to RSVP).

Reminder: FWGS is charged for all RSVP's, so if you RSVP and do not attend you will be contacted concerning payment.

Feared and Actual Impacts of Hydraulic Fracturing on the Carrizo-Wilcox Aquifer in Northwest Louisiana

Douglas Carlson Louisiana Geological Survey, Louisiana State University, Baton Rouge, LA dcarlson@lsu.edu

Abstract

Water chemistry of the Wilcox Aquifer (WA) has been analyzed for over 50 years. This study involved collection and analytical analysis of water chemistry for over twenty different ions from 1136 domestic water supply wells in Bossier, Caddo and De Soto Parishes in 2010 and 2011. This allowed for a detailed spatial view of ion concentrations for a limited time interval. By contrast, USGS water quality data has been collected over decades. Their data set provides information in regard to temporal changes of water quality. With the combination of these two data sets, a conceptual model has been developed that explains the variations of water quality that appear in both time and space. Under the aquifer are several natural gas fields that appear to influence concentrations of methane, and chloride in the overlying WA. Areas above different fields have significant differences of water quality. The number of Haynesville natural gas play wells within a section does not influence the concentration of methane in WA for a section. This indicates that natural gas concentrations in the Wilcox are not typically the result of imperfect construction of oil and gas wells or possible accidents. On the other hand, they could be a result of natural gas seeping up into the overlying Wilcox either through underlying sediments or along fractures and/or faults within the rock between the gas plays and the WA.

Not all variations of water chemistry can be explained by the various gas fields. Other ions, for example iron, calcium, and sodium, appear to vary depending on which of the three sands in the WA is sampled. Concentrations of these ions vary laterally. Surface water bodies also impact water quality. Chloride concentration highs are clustered often near lakes within Caddo and Bossier Parishes, which is an example of the interaction between surface and ground water. It appears that water withdrawals also impact water quality by causing water to move vertically within the Wilcox Aquifer. In addition, these withdrawals cause Red River Alluvial Aquifer (RRAA) water to be drawn into the WA in the cone of depression in southeast-south Caddo Parish. RRAA has higher chloride and sulfate concentrations than WA. The combination of iron and sulfate in higher concentrations plus typical bacterial activity allows the generation of hydrogen sulfide as reported my numerous well owners.

There are trends of water quality for hydraulic fracturing (HF) solution since sampling study of 2010-2011 that could be a concern. Portions of WA southwest and southeast of Shreveport were declared an area that has a temporary ground water emergency in August 18, 2011. The combination of drought and high demand of approximately 3 billion gallons of water used for HF in 2010 and 2011 creating potentiometric declines in WA that caused the condition for the emergency. Between 2011 and 2017, the median volume of water used for an individual well HF has increased from approximately 5 million gallons (Mg) to 20Mg. By 2017 nearly 6 billion gallons of water were used for HF. It would be expected if another boom in drilling and HF similar to 2009-2011 would occur that demand for water could exceed 15 billion gallons. There has been in some cases an increase in concentrations of various toxic compounds such as kerosene, methanol, and isopropanol used within HF solution while the volumes of water used have almost quadrupled. This increases the possible impacts of future accidents. Accidents have happened in the past, approximately once every 1000 wells. Another possible concern is storage of waste water from HF and produced water (PW) from Haynesville production. This flowback water and PW from HF can be a problem when over pressuring the current injection target, Rodessa Formation, causes water to flow upwards into Wilcox and sometimes the surface.

Bio

Dr. Doug Carlson is currently an Associate Professor of Research with the Louisiana Geological Survey. He has been a part of the faculty of the Survey since 2002. His research has focused on aquifer characterization, stream monitoring, groundwater-surface water interactions and use of geophysical techniques in understanding aquifer systems. He has taught introductory geology, environmental geoscience and environmental science at the University of Wisconsin-Milwaukee (1997-2002), introductory astronomy and introductory physics at Ball State University (1989-1990), and introductory physics, earth physics, and statics at the University of Wisconsin-Stout (1984-89). Doug has both a B.S.in Geology (1981) and a B.S. in Geophysics (1981) from the University of Minnesota Institute of Technology, a M.S in Geophysics (1983) from the New Mexico Institute of Mining and Technology, and Ph.D. in Geosciences/Hydrology (2001) from the University of Wisconsin-Milwaukee.